RESUMEN
Low temperature ionic conducting materials such as OH- and H+ ionic conductors are important electrolytes for electrochemical devices. Here we show the discovery of mixed OH-/H+ conduction in ceramic materials. SrZr0.8Y0.2O3-δ exhibits a high ionic conductivity of approximately 0.01 S cm-1 at 90 °C in both water and wet air, which has been demonstrated by direct ammonia fuel cells. Neutron diffraction confirms the presence of OD bonds in the lattice of deuterated SrZr0.8Y0.2O3-δ. The OH- ionic conduction of CaZr0.8Y0.2O3-δ in water was demonstrated by electrolysis of both H218O and D2O. The ionic conductivity of CaZr0.8Y0.2O3-δ in 6 M KOH solution is around 0.1 S cm-1 at 90 °C, 100 times higher than that in pure water, indicating increased OH- ionic conductivity with a higher concentration of feed OH- ions. Density functional theory calculations suggest the diffusion of OH- ions relies on oxygen vacancies and temporarily formed hydrogen bonds. This opens a window to discovering new ceramic ionic conducting materials for near ambient temperature fuel cells, electrolysers and other electrochemical devices.
RESUMEN
Experimental and computational studies of ammonium carbamate have been carried out, with the objective of studying the elastic anisotropy of the framework manifested in (i) the thermal expansion and (ii) the compressibility; furthermore, the relative thermodynamic stability of the two known polymorphs has been evaluated computationally. Using high-resolution neutron powder diffraction data, the crystal structure of α-ammonium carbamate (ND4·ND2CO2) has been refined [space group Pbca, Z = 8, with a = 17.05189â (15), b = 6.43531â (7), c = 6.68093â (7)â Å and V = 733.126â (9)â Å3 at 4.2â K] and the thermal expansivity of α-ammonium carbamate has been measured over the temperature range 4.2-180â K. The expansivity shows a high degree of anisotropy, with the b axis most expandable. The ab initio computational studies were carried out on the α- and ß-polymorphs of ammonium carbamate using density functional theory. Fitting equations of state to the P(V) points of the simulations (run athermally) gave the following values: V0 = 744â (2)â Å3 and bulk modulus K0 = 16.5â (4)â GPa for the α-polymorph, and V0 = 713.6â (5)â Å3 and K0 = 24.4â (4)â GPa for the ß-polymorph. The simulations show good agreement with the thermoelastic behaviour of α-ammonium carbamate. Both phases show a high-degree of anisotropy; in particular, α-ammonium carbamate shows unusual compressive behaviour, being determined to have negative linear compressibility (NLC) along its a axis above 5â GPa. The thermodynamically stable phase at ambient pressure is the α-polymorph, with a calculated enthalpy difference with respect to the ß-polymorph of 0.399â kJâ mol-1; a transition to the ß-polymorph could occur at â¼0.4â GPa.
Asunto(s)
Dióxido de Carbono , Neutrones , Carbamatos , Difracción de Polvo , PolvosRESUMEN
PURPOSE: Deep sedation is sometimes needed in acute respiratory distress syndrome. Ketamine is a sedative that has been shown to have analgesic and sedating properties without having a detrimental impact on hemodynamics. This pharmacological profile makes ketamine an attractive sedative, potentially reducing the necessity for other sedatives and vasopressors, but there are no studies evaluating its effect on these medications in patients requiring deep sedation for acute respiratory distress syndrome. MATERIALS AND METHODS: This is a retrospective, observational study in a single center, quaternary care hospital in southeast Texas. We looked at adults with COVID-19 requiring mechanical ventilation from March 2020 to September 2020. RESULTS: We found that patients had less propofol requirements at 72 h after ketamine initiation when compared to 24 h (median 34.2 vs 54.7 mg/kg, p = 0.003). Norepinephrine equivalents were also significantly lower at 48 h than 24 h after ketamine initiation (median 38 vs 62.8 mcg/kg, p = 0.028). There was an increase in hydromorphone infusion rates at all three time points after ketamine was introduced. CONCLUSIONS: In this cohort of patients with COVID-19 ARDS who required mechanical ventilation receiving ketamine we found propofol sparing effects and vasopressor requirements were reduced, while opioid infusions were not.
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COVID-19/epidemiología , Sedación Profunda , Hipnóticos y Sedantes/administración & dosificación , Ketamina/administración & dosificación , Respiración Artificial , Síndrome de Dificultad Respiratoria/epidemiología , Adulto , Anciano , Anciano de 80 o más Años , Analgésicos Opioides/uso terapéutico , COVID-19/terapia , Utilización de Medicamentos/estadística & datos numéricos , Femenino , Humanos , Hidromorfona/uso terapéutico , Masculino , Persona de Mediana Edad , Norepinefrina/uso terapéutico , Propofol/uso terapéutico , Síndrome de Dificultad Respiratoria/terapia , Estudios Retrospectivos , Texas/epidemiologíaRESUMEN
Hypoxemic respiratory failure is a common manifestation of COVID-19 pneumonia. Early in the COVID-19 pandemic, patients with hypoxemic respiratory failure were, at times, being intubated earlier than normal; in part because the options of heated humidified high flow nasal cannula (HFNC) and non-invasive ventilation (NIV) were considered potentially inadequate and to increase risk of virus aerosolization. To understand the benefits and factors that predict success and failure of HFNC in this population, we evaluated data from the first 30 sequential patients admitted with COVID-19 pneumonia to our center who were managed with HFNC. We conducted Cox Proportional Hazards regression models to evaluate the factors associated with high flow nasal cannula failure (outcome variable), using time to intubation (censoring variable), while adjusting for comorbidities and immunosuppression. In the majority of our patients (76.7%), the use of HFNC failed and the patients were ultimately placed on mechanical ventilation. Those at increased risk of failure had a higher sequential organ failure assessment score, and at least one comorbidity or history of immunosuppression. Our data suggest that high flow nasal cannula may have a role in some patients with COVID-19 presenting with hypoxemic respiratory failure, but careful patient selection is the likely key to its success.
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COVID-19/complicaciones , Cánula/efectos adversos , Ventilación no Invasiva/efectos adversos , Terapia por Inhalación de Oxígeno/efectos adversos , Pandemias , Insuficiencia Respiratoria/terapia , Anciano , Anciano de 80 o más Años , COVID-19/epidemiología , Falla de Equipo , Femenino , Humanos , Masculino , Persona de Mediana Edad , Ventilación no Invasiva/instrumentación , Terapia por Inhalación de Oxígeno/instrumentación , Insuficiencia Respiratoria/etiología , SARS-CoV-2RESUMEN
An apparatus is described for the compression of samples to â¼2â GPa at temperatures from 80 to 300â K, rapid chilling to 80â K whilst under load and subsequent recovery into liquid nitro-gen after the load is released. In this way, a variety of quenchable high-pressure phases of many materials may be preserved for examination outside the high-pressure sample environment, with the principal benefit being the ability to obtain high-resolution powder diffraction data for phase identification and structure solution. The use of this apparatus, in combination with a newly developed cold-loadable low-temperature stage for X-ray powder diffraction (the PheniX-FL), is illustrated using ice VI (a high-pressure polymorph of ordinary water ice that is thermodynamically stable only above â¼0.6â GPa) as an example. A second example using synthetic epsomite (MgSO4·7H2O) reveals that, at â¼1.6â GPa and 293â K, it undergoes incongruent melting to form MgSO4·5H2O plus brine, contributing to a long-standing debate on the nature of the high-pressure behaviour of this and similar highly hydrated materials. The crystal structure of this new high-pressure polymorph of MgSO4·5H2O has been determined at 85â K in space group Pna21 from the X-ray powder diffraction pattern of a sample recovered into liquid nitro-gen and is found to differ from that of the known ambient-pressure phase of MgSO4·5H2O (pentahydrite, space group ), consisting of corner-sharing MgO6-SO4 ion pairs rather than infinite corner-sharing chains.
RESUMEN
Single crystals of glycine zinc sulfate penta-hydrate [systematic name: hexa-aqua-zinc tetra-aquadiglycinezinc bis-(sulfate)], [Zn(H2O)6][Zn(C2H5NO2)2(H2O)4](SO4)2, have been grown by isothermal evaporation from aqueous solution at room temperature and characterized by single-crystal neutron diffraction. The unit cell contains two unique ZnO6 octa-hedra on sites of symmetry -1 and two SO4 tetra-hedra with site symmetry 1; the octa-hedra comprise one [tetra-aqua-diglycine zinc]2+ ion (centred on one Zn atom) and one [hexa-aqua-zinc]2+ ion (centred on the other Zn atom); the glycine zwitterion, NH3+CH2COO-, adopts a monodentate coordination to the first Zn atom. All other atoms sit on general positions of site symmetry 1. Glycine forms centrosymmetric closed cyclic dimers due to N-Hâ¯O hydrogen bonds between the amine and carboxyl-ate groups of adjacent zwitterions and exhibits torsion angles varying from ideal planarity by no more than 1.2°, the smallest values for any known glycine zwitterion not otherwise constrained by a mirror plane. This work confirms the H-atom locations estimated in three earlier single-crystal X-ray diffraction studies with the addition of independently refined fractional coordinates and Uij parameters, which provide accurate inter-nuclear X-H (X = N, O) bond lengths and consequently a more accurate and precise depiction of the hydrogen-bond framework.
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Anti-N-methyl-d-aspartate receptor encephalitis (NMDARE) is characterized by a constellation of psychiatric, neurologic, autonomic, and cardiopulmonary manifestations. Although patients typically recover with appropriate treatment, they commonly require weeks to months of inpatient care, including prolonged stays in critical care units. This case series not only advocates for consideration of the disease in the appropriate context but also specifically highlights the distinct challenges intensivists encounter caring for patients with NMDARE. With a greater knowledge of the nuances and sequelae of NMDARE, critical care specialists will be better equipped to anticipate and manage the potentially life-threatening complications of the disease.
Asunto(s)
Encefalitis Antirreceptor N-Metil-D-Aspartato/terapia , Cuidados Críticos/tendencias , Glucocorticoides/administración & dosificación , Inmunoglobulinas Intravenosas/administración & dosificación , Intercambio Plasmático/métodos , Respiración Artificial/métodos , Encefalitis Antirreceptor N-Metil-D-Aspartato/diagnóstico , Líquido Cefalorraquídeo/química , Terapia Cognitivo-Conductual/métodos , Cuidados Críticos/normas , Relación Dosis-Respuesta a Droga , Femenino , Humanos , Factores Inmunológicos/administración & dosificación , Inyecciones Intravenosas , Receptores de N-Metil-D-Aspartato/inmunología , Receptores de N-Metil-D-Aspartato/metabolismo , Adulto JovenRESUMEN
An outbreak of hepatitis E virus (HEV) began in October 2007 in northern Uganda. To determine risk factors and sources for ongoing transmission, we conducted both a case-control study and an environmental investigation. A case patient was defined as having serologic evidence of HEV infection, whereas controls were seronegative. We identified risk factors for infection by univariable and multivariable analyses using conditional logistic regression. Several water sources were tested for HEV RNA. Among 112 cases and 145 controls, storage of drinking water in large-mouthed vessels (adjusted odds ratios [AOR] = 2.83; 95% confidence interval [CI] = 1.16-6.94) and washing hands in a group basin (AOR = 1.90; 95% CI = 1.07-3.38) were associated with HEV infection. HEV RNA was detected from communal hand-rinse and surface-water samples. The epidemiologic and environmental water-testing results suggest that household-level factors played an important role in the transmission of HEV-modalities that have been previously underappreciated.
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Brotes de Enfermedades , Hepatitis E/epidemiología , Adolescente , Adulto , Estudios de Casos y Controles , Niño , Preescolar , Virus de la Hepatitis E/genética , Virus de la Hepatitis E/inmunología , Virus de la Hepatitis E/aislamiento & purificación , Humanos , Lactante , Recién Nacido , Persona de Mediana Edad , Oportunidad Relativa , ARN Viral/aislamiento & purificación , Factores de Riesgo , Uganda/epidemiología , Microbiología del Agua , Adulto JovenRESUMEN
In October 2007, an epidemic of hepatitis E was suspected in Kitgum District of northern Uganda where no previous epidemics had been documented. This outbreak has progressed to become one of the largest hepatitis E outbreaks in the world. By June 2009, the epidemic had caused illness in >10,196 persons and 160 deaths.